The PHP link is fairly normal, and you will see more like it if you pay close attention to the URLs in your browser window.

What the link does, is, it calls the script main.php, with the argument video=1768812741, which can be translated in understandable English as: 'Hey file main.php, please load a video with the following ID (identifier): 1768812741'. So the URL just loads a video with a predefined ID.